He said two of the men had no criminal history, while one had a minor record for failing to display L plates in 2007.

"Other than that there's no criminal history or background, certainly no bail or anything like that applying in this case," he said.

Mr Ashton said the trio's use of encrypted communications made it difficult for police and intelligence agencies to track their activities.

Home Affairs Minister Peter Dutton has been pushing for new laws to make it easier for authorities to access messages sent through encrypted messaging apps.

"We have a bill before the parliament that provides the appropriate safety mechanisms, privacy protections in place, but it allows police and ASIO to do their jobs in relation to these terrorist investigations," he said on Tuesday.

The Assistant Commissioner of Victoria Police's Counter Terrorism Command, Ross Guenther, said the proposed changes would make an "enormous difference" to terrorism investigators.

"The likes of Telegram and WhatsApp are very commonly used as a mechanism of communication between plotters," he told ABC Radio Melbourne.

"Accessibility to that type of information is going to allow us to disrupt at a much earlier time.

"Some of these investigations we undertake for 18 months and two years, and that's because it takes us so long to get in front of them in terms of understanding how they communicate."

Consequences could have been 'chilling'

AFP Assistant Commissioner Ian McCartney said, if found guilty, the men could face life in prison.

"We'll allege the consequences would have been chilling, with … a potential significant loss of human life," Assistant Commissioner McCartney said.

He said the men's passports were cancelled because of concerns they intended to travel to a "conflict zone".

"At the time the decision was made, the concern was that they would travel offshore and may be involved in terrorist activity offshore," Assistant Commissioner McCartney said.

He said it was important to note that authorities did not believe the men were directed by ISIS.

"It's an attack that's been inspired by ISIS, driven by the propaganda machine, and unfortunately people are still listening to that propaganda machine."

Assistant Commissioner Guenther said when radicalised people had their passports cancelled, they often turned their attention to organising attacks in their home country.

"When people are prevented from travelling or it's difficult to get to the conflict zone, often the view will be, 'Well I'll change tack and commit an act in the country [in] which I live'. We've seen that all over the world," Assistant Commissioner Guenther said.

'They don't like Islamic State'

Armagan Eriklioglu, who said he was the father of the older men, said his sons were neither violent nor inspired by IS.

"They don't even know how to use a weapon, they didn't even go to the army," he told reporters outside the family home in Campbellfield, where he said the younger son still lived.